The field of the present invention is water sports boards such as surfboards and the construction of fins therefor.
A variety of boards have been developed over the years for water sports activities including the use of such boards in ocean surf. Typically, such boards are of lightweight material so as to be relatively rigid. Frequently, a coating of glass fiber reinforced resin encases the board. For stability and control, such boards typically include fins. The fins are placed near the back of the board on the underside thereof to extend downwardly into the supporting water. Fins come in a variety of shapes and sizes according to the preferences of the designers and users. The fins are frequently positioned normal to the surface of the board but have also been used as angles to the normal as well.
The fin structures are rigidly mounted to the boards and are themselves rigid. The rigidity of a fin has been generally considered essential to avoid oscillations and cavitation, to insure control and to avoid directional instabilities.
The structural requirements and orientation of such fins on water sports boards and their use in a typically turbulent water environment create a hazardous condition. In the turbulence, the board itself can be driven by the water with injurious force. Some efforts have been made to cushion the leading portion of the board which is not subject to the same rigidity requirements of a fin. Rigid fins are typically of smaller cross section and are driven by the same forces driving the board in turbulent surf. Consequently, fins have a greater propensity to inflict injury to the human body. They are typically more knife-like, they extend clear of the supporting board and they are so rigidly attached to the supporting board that they are driven with the same momentum and force. Injuries due to fins are understood to be substantial in number on an ongoing weekly basis in the United States.